In Vitro and In Vivo Induction of Antiangiogenic Activity by Plasminogen Activators and Captopril

Background: Many antiangiogenic molecules are proteolyti-cally cleaved from larger plasma proteins. For example, plasminogen activators cleave plasminogen into plasmin, and plasmin is converted into angiostatin in the presence of sulfhydryl donors. We thus investigated whether the antian-giogenic activity in plasma could be increased by treatment with recombinant tissue plasminogen activator (rt-PA) and the sulfhydryl donor captopril. Methods: Human plasma was treated with rt-PA (10 µg/mL) and/or captopril (1 µM). An-giogenesis was measured in vitro by human endothelial cell tube formation and endothelial cell proliferation and in vivo in mice with the Matrigel plug assay. Angiostatin was re-moved from treated plasma by affinity chromatography, im-munoprecipitation, or ion-exchange chromatography, and the antiangiogenic activity of the depleted plasma was as